The present invention relates to an electric-acoustic transducer having a moving magnet structure and transducing method thereof, and more particularly to an improved electric-acoustic transducer and electric-acoustic transducing method in which a driving coil generating an alternating magnetic field in accordance with an audio signal is fixed to a frame, and a permanent magnet generating a non-alternating magnetic field is displaced by the alternating magnetic field to displace a vibrating diaphragm, thereby producing a sound corresponding to the audio signal.
A micro-speaker is a kind of an electric-acoustic transducer which transduces an electric signal of a variety of electronic appliances, requiring a transmission of a sound, into an audio sound. A conventional micro electric-acoustic transducer, (hereinafter, referred to as xe2x80x9cmicro-speakerxe2x80x9d), usually is classified into an electrodynamic type speaker and an electromagnetic type speaker.
The electrodynamic type speaker is of a structure in which the attraction and repulsion caused due to a reaction of a non-alternating (direct current: DC) magnetic flux generated in a fixed magnetic circuit upon an alternating (alternating current: AC) rotation magnetic flux generated in a moving coil movable in an upward and downward direction vibrate both the vibrating diaphragm and the moving coil upwardly and downwardly to produce a sound. That is, the electrodynamic type speaker is a speaker in which the permanent magnet is fixed and the moving coil is moved, so that a sound is generated.
However, the electrodynamic type speaker has disadvantages that in the case where it is manufactured in a micro form in order to apply to a notebook computer, a mini-cassette tape player, and a mobile communication terminal, etc., it is impossible to reproduce an expansion of the ranges of a low-pitched sound and a high-pitched sound necessary for portable electronic appliances in terms of a structure of a speaker, and a breaking of a coil wire for supplying electric energy to the moving coil vibrating upwardly and downwardly makes it impossible to both receive a high input and secure sufficient space to allow for an upward and downward vibration of the moving coil to receive a high output.
For reference, in a micro-speaker currently on the market, a rated input of a product whose diameter is less than 20 mm is 0.01 (W)xcx9c0.1 (W).
In addition, in the case where a speaker is embedded in a main PCB of a set, because a structure allowing the speaker to be automatically embedded in the main PCB with respect to all directions of 360 degrees while allowing the speaker to be electrically connected with the PCB has not been designed yet, automation in operation is not completely performed and a great deal of effort and time is needed when embedding the speaker in the PCB.
Meanwhile, in the electromagnetic type speaker, when the constant attraction of the permanent magnet reacts upon the alternating magnetic flux of alternating current properties generated in the moving coil to adjust a strength of the magnetic field, both the permanent magnet and the coil have been fixed so that a tension of the vibrating diaphragm itself causes a displacement of the vibrating diaphragm, thereby producing a sound.
However, the above electromagnetic type speaker has an inadequate coupling structure in which embedding of the speaker in a set always requires a bonding and soldering process of the speaker to the main PCB of the set. Further, in the electromagnetic type speaker, the vibrating diaphragm cannot freely vibrate upwardly and downwardly, and the upper and lower space necessary for a vibration of the vibrating diaphragm is very narrow, which makes it impossible to reproduce a sound of a broad band and a high input.
There is therefore a need in the art for a micro-speaker that can reproduce a sound of a broad band, receive a high input, and can be automatically embedded in a PCB of a set in all directions of 360 degrees without a soldering process in order to realize a multipurpose mini personal information processing terminal in the near future.
The present invention has been made in view of the above mentioned problems involved in the conventional micro electric-acoustic transducer, i.e., micro-speakers, and an object of the invention is to provide an electric-acoustic transducer and transducing method thereof in which in a state in which a driving coil is fixed to a frame, generation of an alternating magnetic field by an electric driving signal of the outside causes displacement of a permanent magnet, supported by a vibrating diaphragm, generating a non-alternating magnetic field, so that the vibrating diaphragm is also displaced, thereby producing a sound corresponding to the electric signal.
Another object of the invention is to provide an improved micro-speaker which includes a disc-shaped moving magnet in which a magnetic circuit is coupled to a vibrating diaphragm or a moving magnet serving as the vibrating diaphragm, and a fixed coil.
Still another object of the invention is to provide an improved micro-speaker which can receive a broad band, a high input and a high output covering functions for reproducing sounds outputted from various portable electronic appliances and all sounds of a receiver and a micro-speaker, as a single unit of a small size.
Still another object of the invention is to provide an improved micro-speaker in which the above-mentioned functions are implemented and automatic mounting/coupling of the speaker in all directions 360 degrees to a PCB of a set can be performed by simply applying a pressure to the speaker, and which has a structure allowing for automation of a process of manufacture.
Yet another object of the invention is to provide an improved micro-speaker which has a new structure formed of a plurality of moving magnets or a single moving magnet and a plurality of fixed coils, can be automatically embedded on the surface of a PCB of a set in all directions of 360 degrees, and can reproduce a sound of a broad band range, and receive a high input.
In accordance with one aspect, the present invention provides an electric-acoustic transducer comprising: at least one fixed coil adapted to generate an alternating magnetic field upon externally receiving an electrical drive signal; a frame having a recessed structure for centrally receiving and supporting the fixed coil; at least one moving permanent magnet disposed over the fixed coil while being spaced from the fixed coil by a desired vertical distance in such a fashion that it is vertically movable, the moving permanent magnet serving to generate a non-alternating magnetic field; and a vibrating diaphragm supported by an upper end of the frame at a peripheral portion thereof, the vibrating diaphragm supporting the permanent magnet by a central portion thereof; whereby the vibrating diaphragm vibrates vertically in accordance with an interaction between the alternating magnetic field generated from the fixed coil and the non-alternating magnetic field generated from the permanent magnet.
In accordance with another aspect, the electric-acoustic transducer of the present invention further comprises: a printed circuit board buried in a bottom portion of the frame, the printed circuit board having a pair of electrode patterns, to which a pair of coil lines extending from the fixed coil are connected, respectively, so that the printed circuit board serves as a terminal plate, the electrode patterns being arranged at different radial positions with respect to the center of the fixed coil; a pair of electrodes each having one end mounted to an associated one of the electrode patterns and the other end extending downwardly from the printed circuit board while having an elasticity, the drive signal being applied to the electrodes; and snap coupling means extending downwardly from the bottom portion of the frame inside the electrodes, the snap coupling means being coupled, in a snapped fashion, to a coupling hole formed at a main printed circuit board mounted to an appliance, to which the transducer is applied, the main printed circuit board generating the drive signal and having a pair of concentric annular electrode pads arranged at different radial positions with respect to the center of the coupling hole, the radial positions of the annular electrode pads corresponding to the radial positions of the electrodes, respectively.
In accordance with one aspect, the present invention provides an electric-acoustic transducing method comprising the steps of: externally applying an electrical drive signal to a fixed coil fixed to a frame, thereby generating alternating magnetic field varying in accordance with the electrical drive signal; and vertically vibrating a moving permanent magnet adapted to generate non-alternating magnetic field of a desired magnitude and supported to a vibrating diaphragm in such a fashion that it is vertically movable by the vibrating diaphragm, thereby generating sound.
In accordance with the present invention, the electric-acoustic transducer has a sound reproducing capacity of a broad band range (300 Hz xcx9c16 KHz for a product having a diameter of 20 mm) necessary for various portable electronic appliances, a receiver and a micro-speaker, and can receive a high input (a rated input of 3xcx9c5 W for a product having a diameter of 20 mm). Further, in the electric-acoustic transducer, automatic mounting of the speaker in all directions 360 degrees to a PCB of a set can be performed while accomplishing complete automation of a process of manufacture without requiring a soldering and bonding process.